Embodiments of the present invention relate to a method for pipeline inspection, and more particularly, a method for in-line detection of anomalies such as cracks and/or corrosion in or near dented regions of a pipeline.
It is known to carry out inspection of a pipeline using an inspection apparatus (commonly referred to as a pipeline “pig”), which travels inside the pipeline and includes inspection sensors arranged for measuring or detecting defects in the wall of the pipeline.
Many conventional in-line inspection techniques require accurate mechanical alignment of inspection sensors with respect to the pipe wall in order to maintain a suitable level of inspection sensitivity. A problem occurs if the pipeline includes a dented region or other physical anomaly. A significant factor is that pipeline dents tend to have an arbitrary shape and are difficult for inspection apparatus to negotiate mechanically. This mechanical difficulty can translate into an inspection difficulty, particularly if desired alignment between the inspection sensors and the surface under inspection is compromised as the apparatus passes through a dented region at speed.
It is not uncommon, therefore, for the general location of a dented region within a pipeline to be identified and then classified as a region of limited inspection, due to the potential unreliability of inspection data from that location.
Otherwise, it is known to use a dimensional tool to determine the specific geometry of a particular dent, and to then carry out a probability analysis for the likely presence of cracks or corrosion as a function of the specific geometry. However, it will be understood that such indirect analysis techniques are prone to error and may even leave potentially serious defects undetected.
A method for pipeline inspection which overcomes or mitigates one or more of the above problems, or other disadvantages or problems associated with conventional methods for inline inspection of pipelines would be desirable.